Oxidative stress in Cohen diabetic rat model by high-sucrose, low-copper diet: inducing pancreatic damage and diabetes.

Increased oxidative stress contributes to the development and progression of both types of diabetes mellitus (DM) and its complications. In the Cohen diabetic (CD) rats, a known genetic model of nutritionally induced type 2 DM, a high-sucrose, low-copper diet (HSD) induces within 4 weeks DM in the sensitive (CDs) rats but not in the resistant (CDr) rats. To assess the possible involvement of oxidative stress in the induction of DM, we studied the effect of HSD on the tissue levels of antioxidants and the extent of oxidative injuries in these animals in comparison with the regular outbred strain of nondiabetic Sabra rats. The specific aims were to investigate, at the onset of HSD-induced DM, (1) the extent of oxidative injury, as reflected by levels of malondialdehyde and protein carbonyl groups; (2) the overall antioxidant capacities to cope with increased oxidative stress; and (3) the modification of oxidative damage biomarkers in various tissues of CDr, CDs, and Sabra rats. Female CDs, CDr, and Sabra rats were fed regular diet or HSD for 4 to 5 weeks; and several parameters of oxidative injuries and antioxidant levels were determined. Changes in the levels of nonenzymatic low-molecular weight antioxidants (LMWAs) were measured by cyclic voltammetry and oxygen radical absorbance capacity. The activities of the antioxidant enzymes superoxide dismutase and catalase were measured. Oxidative damage was evaluated by measuring lipid peroxidation and protein oxidation. (1) In all animals fed HSD, the levels of LMWAs were decreased in most organs, although not plasma. (2) A significant difference was consistently found in antioxidant enzymes' activities in the pancreas of HSD-fed CDs rats, but not in other tissues. (3) The activities of superoxide dismutase and catalase and the levels of malondialdehyde and protein carbonyl group increased, whereas the levels of LMWAs decreased, in the pancreas of HSD-fed CDs rats. In the CD rats that develop DM when fed HSD, the pancreas showed susceptibility to oxidative stress-induced injuries. Thus, enhanced oxidative stress seems to play a role in the pathogenesis of DM in this strain.

Nitroxide radicals protect cultured rat embryos and yolk sacs from diabetic-induced damage.

BACKGROUND: Diabetic teratogenicity relates, partly, to embryonic oxidative stress and the extent of the embryonic damage can apparently be reduced by antioxidants. We investigated the effects of superoxide dismutase-mimics nitroxides, 2,2,6,6-tetramethyl piperidine-N-oxyl (TPL) as an effective antioxidant, on diabetes-induced embryopathy. METHODS: Embryos (10.5 day old) and their yolk sacs from Sabra female rats were cultured for 28 h in the absence or in the presence of nitroxides at 0.05-0.4 mM in control, diabetic subteratogenic, or diabetic teratogenic media, and monitored for growth retardation and congenital anomalies. The oxidant/antioxidant status was examined by oxygen radical absorbance capacity and lipid peroxidation assays, whereas the yolk sac function was evaluated by endocytosis assay. RESULTS: Diabetic culture medium inhibited embryonic and yolk sac growth, induced a high rate of NTDs, reduced yolk sac endocytosis and embryonic antioxidant capacity, and increased lipid peroxidation. These effects were more prominent in the embryos with NTD compared to those without NTD. TPL added to diabetic teratogenic medium improved embryonic and yolk sac growth, reduced the rate of NTDs, and improved yolk sac function. The oxidant/antioxidant status of embryos was also improved. TPL at 1 mM did not damage the embryos cultured in control medium. CONCLUSIONS: In diabetic culture medium, oxidative damage is higher in the malformed rat embryos compared to those without anomalies; the nitroxide provides protection against diabetes-induced teratogenicity in a dose-dependent manner. The yolk sac damage, apparently caused by the same mechanism, might be an additional contributor to the embryonic damage observed in diabetes.

Alterations in the expression of antioxidant genes and the levels of transcription factor NF-kappa B in relation to diabetic embryopathy in the Cohen diabetic rat model.

BACKGROUND: We have previously shown that oxidative stress is important in the pathogenesis of diabetes-induced anomalies in Cohen Diabetic sensitive (CDs) rat embryos and seems to interplay with genetic factors. We investigated the role of genetic factors related to the antioxidant defense mechanism in CDs rat embryos. METHODS: We studied 11.5- and 12.5-day embryos of Cohen Diabetic resistant (CDr) and CDs rats that were fed a regular diet (RD), and hence not diabetic, compared to rats fed a high-sucrose low-copper diet (HSD) where only the CDs animals became diabetic. Embryos were monitored for growth and congenital anomalies. mRNA of catalase (CAT), glutathione peroxidase (GSHpx), CuZn-SOD (SOD-superoxide dismutase), and Mn-SOD and the extent of nuclear factor kappa B (NF-kappaB) activation were assessed. RESULTS: Embryos of CDs dams fed RD were significantly smaller and had an increased rate of NTDs compared to embryos of CDr dams fed RD. When CDs dams were fed HSD, >50% of the CDs embryos were dead and 44% of the live embryos had NTDs. Live 11.5-day old embryos of CDs dams fed RD had a statistically significant increase in CAT, CuZn-SOD, and GSHpx mRNA levels compared with the levels in the CDr embryos from dams fed RD. CDs embryos from dams fed HSD showed significant overactivation of NF-kappaB compared with CDr embryos from dams fed HSD (in which activation was decreased), without any increase in the expression of SOD, CAT, and GSHpx. CONCLUSIONS: This study demonstrates that one of the genetic differences between the CDr and CDs strains fed RD is an increased expression of genes encoding for antioxidant enzymes in the CDs but inability for upregulation in diabetes. In addition, while activation of NF-kappaB is decreased in CDr on HSD, it is increased in the CDs. These differences may play a role in the increased sensitivity of the CDs embryos to diabetic-induced teratogenicity.